This is clearly a case of measure Zs and deduct Ze for the continuity no one surely does it the other way on a Periodic. So OP are there no insulation resistance readings.
I think what you state is spot on ,however,he can only prove its fudged if new tests contradict the readings he has been given
I am making the point to him that what he has been given is a legitimate if unusual means of obtaining Zs on a periodic but there are 2 ways to skin the cat